OldMarine Posted April 24, 2017 Posted April 24, 2017 (edited) I'll give an example I know right off the top of my head that involves 3 springs but the concept is the same.A Wilkins 375 #1 check from the factory exerts a constant closing pressure of 8+ psi across the check no matter the flow rate or position between open and closed positions. The only exception is during the first 1% of travel during opening which is referred to as opening take-up in the literature. Single spring devices aren't measured for this for some reason but my test gauges show it every time as a spike in differential pressure immediately after loading the check with forward pressure. The 8psi mentioned above is constant across the normal range of travel of the spring from just past take-up to complete metal on metal compression. There may be a difference but I'll be dogged if i understand it. Durham is out. Edited April 24, 2017 by OldMarine
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 (edited) I'd expect that phenomenon is only valid with RPZ backflow preventers due to either the velocity of the flow helps to keep the valve open during use or the initial 1% of the valve stroke has less back pressure to assist the spring. Edited April 24, 2017 by NeighborJ
lloyd Posted April 24, 2017 Posted April 24, 2017 "Mon offre de paix" lasts 'til bedtime. <shrug> Lloyd
lloyd Posted April 24, 2017 Posted April 24, 2017 (edited) Patrick, A Wilkins 375 2-1/2" backflow preventer shows (from their spec's) a variable pressure loss across the valve from 7psi at zero flow to about 11psi at 10gpm, and increasing to 17psi at 320gpm. That's not 'constant drop', and indicates the flow itself is aiding in keeping the valve open and the springs compressed. The springs cannot exert a constant force from initial load to full-solid compression. That violates basic physics. Their next-larger valve shows an even lower opening pressure, then constantly rising to the peak flow rating of 480gpm (18.5psi) Lloyd Edited April 24, 2017 by lloyd
lloyd Posted April 24, 2017 Posted April 24, 2017 Oh... Patrick, to explain further... When the valve is closed, it's simply 'static pressure' (piston force) across the face of the valve. As flow increases, there's also the 'impact force' (inertial effect) of the water's HITTING that valve face at (pretty high) velocity. You know that when you hold an ounce of water in your hand, you feel an ounce. But when that same ounce of water hits your hand at 100fps, it smacks into you like a well-hit golf ball! It's the same reason it doesn't hurt to jump into a pool, but hurts like hell when you belly-flop from a high-dive. Lloyd
lloyd Posted April 24, 2017 Posted April 24, 2017 (edited) 48, 47, 46... Sorry... that's for a guy who owns NO books. That might be too tough. Let's try: 45 minutes. Lloyd Edited April 24, 2017 by lloyd
OldMarine Posted April 24, 2017 Posted April 24, 2017 No need to get ugly. I said I didn't understand and stated I was ducking out. I've clearly stated that I'm mathematically dyslexic and I'll live with it.
lloyd Posted April 24, 2017 Posted April 24, 2017 (edited) That wasn't directed at you, Patrick. All I responded to that you asked about was explain the math for spring rate, and to explain about the check-valve mechanism you asked about. And politely. The 'deadline' was about 'my offer of peace' -- to NeighborJ, and in a post separate from the math and valve things. I happen to know you own books... so why would I say that to you, of all people? In fact, I consider you a friend, or I wouldn't have responded elsewhere to you about the upcoming meeting you were interested in. I said "ask Bradley", because he's trying to figure out how to come, too (and he's a member). I'm probably just being stubborn, but when someone (not you, NeighborJ) does something I took as offensive (right or wrong), and I return saying, "OK, let's make peace", and they don't even bother, then I set a deadline beyond which it won't BE mended. I'm ex-combat military, like you. You draw your lines, and you hold them, even for 'trivial' things. You're my friend, Patrick. You mistook my comments which were not directed at you. Lloyd Edited April 24, 2017 by lloyd
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 I was wondering what"Mon offer de paix" meant. I'm clueless here so I don't know what you want me to do. Is there a deadline for something? Maybe I missed something I'll go back and reread the thread.
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 I think you want me to ask how to use the springs in the press, yes? I do, please, when or if you get the chance.
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 Lloyd if I had understood what you were sayin then I'd have done whatever needed doin. I don't watch enough old war movies to be able to communicate with you. I never had ill intention toward you and still don't. It's not worth changing names because it won't overcome the apparent language barrier and will happen again.
lloyd Posted April 24, 2017 Posted April 24, 2017 Neighbor, I won't discuss the rocket thing with you anymore. The fact that you're not even curious enough to wonder what I meant (and maybe do a quick on-line search to see) is clear. You certainly didn't have any trouble looking up the valve! The fact that you don't own even one pyro book (and bragged about it on another site), while at the same time pretending to 'be interested' in the art says even more. I just had a lengthy conversation with a gentleman for whom curiosity about this art is his primary driver. That mode of thought is what furthers our endeavors and improves our insights and processes. I'm always interested in trying to help someone who's genuinely curious about things -- and it turns out they very often know more or have better insights into the processes than do I, so I learn from those interactions as often as I do to help others learn. I expressed in private communications to another user here that I "do the thinking" for a number of people in my business circles for whom the effort to do it themselves is just too much bother. I have quite enough of that to keep me 'satisfied'. I never asked you to change your on-line moniker (better look up that word!). I asked if I might address you by your first name. You refused -- or didn't care, and that amounts to the same thing. I shouldn't even have bothered to post this explanation. But anyone deserves to understand why I take the positions I do, if it affects our relationship even a little. Lloyd 1
lloyd Posted April 24, 2017 Posted April 24, 2017 "Evenin' Lloyd!"-----------------Ah! The timing of that tells me much!
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 Thanks for the explanation Lloyd. I've never been good at not offending people and you are correct on several points so I will make every attempt to correct those points in the future. I'm sorry to those I may have upset.
lloyd Posted April 24, 2017 Posted April 24, 2017 (edited) Neighbor, This doesn't rule out our participating together in other conversations. I'm really not an ogre. I'm just done with this subject. I wouldn't advise someone to do something I knew to be dangerous. I recently had a client ask me to repair a foot pedal actuated press. I was willing to do the repairs (and even sell him such 'extra parts' [NOT plumbed-in] as he wished to buy), but I would never provide any press connected to such an affair. It's too likely to result in an injury. That's not only because of the potential liability, but also because I want people to be safe. I don't give service or advice I consider to be dangerous. I have a fair bit of experience with using and building pyro tooling, and have had to comply with mil-spec and/or OSHA standards on everything I make. On the other matter -- I like people, not "internet nyms". I very much enjoy addressing people by - and being addressed by - 'given names'. I don't need or even desire to know your surname unless you wish to provide it, but your first name would be nice to have when we're communicating. Lloyd Edited April 24, 2017 by lloyd
NeighborJ Posted April 24, 2017 Author Posted April 24, 2017 My name is Jason and I'm sorry I didn't understand that you were asking for it until today. The wording of it seemed as if it was a joke, suggesting that neighborJ was my real name.
MrB Posted April 25, 2017 Posted April 25, 2017 The fact that you're not even curious enough to wonder what I meant (and maybe do a quick on-line search to see) is clear. To be fair, i Googled "Mon offre de paix" and all i got was weird french, and something about Hitler. To get any idea it was an peace offering, i had to go find an online translator. And for what it's worth. My name is Björn. But people call me B. Your call, but i'd suggest you shout "B!" if it's ever an emergency, if anyone shouts "Björn!" i generally ignore it, or, continue what i'm doing while lazily looking for that other fella with "my" name.B!
lloyd Posted April 25, 2017 Posted April 25, 2017 B!,It's what you 'go by' that I want to know. If your name was Kenneth, but you went by the name "Ned", I'd call you Ned. My mom's proper first name was Mary, but she went by her middle name, Kathleen, and was called "Kay". Since you were Born as Bjorn, you have to 'deal with it', anyway, huh? <grin> Take care, B. Lloyd
MrB Posted April 25, 2017 Posted April 25, 2017 Since you were Born as Bjorn, you have to 'deal with it', anyway, huh? <grin> It generally only takes a few failed attempts to communicate with me before people figure it out. But yeah. "Björn" being a (to) common name means there is always a bunch of us in the same place, where ever we go. We all deal with it, in different ways. I think we were 3 in my elementary school class, so it's been B ever since.B!
NeighborJ Posted April 30, 2017 Author Posted April 30, 2017 Spent all day making tooling in anticipation of this project. 4-1# whistle tools to start with and left spots to expand up to 9. I will need to buy some more AL bar stock to make them but I'll wait until I see how well this whole thing will work first. I rummaged thru all my supplies and found almost everything I'll need to build the press, minus about 100 bucks worth of parts I ordered, which should arrive Monday.
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